This invention relates to apparatus for producing striped or striated coatings of paint or the like on extended solid surfaces. In an important particular sense, it is directed to the production of longitudinally striped surface coatings on elongated strip articles, and especially to the provision of coatings wherein the lines or stripes vary in spacing and lateral position along the length of the coated article, for example to create a pattern simulating the appearance of natural wood grain.
By way of specific illustration, detailed reference will be made herein to the coating of sheet material (e.g. aluminum) in greatly elongated strip form, as used for making siding panels for cladding exterior building walls, it being understood, however, that the invention in its broader aspects embraces the coating of other types of articles and surfaces as well.
In the production of siding panels from metal strip, at least one major surface of the strip is first coated with paint, and the strip is then formed and cut into individual panels, which are commonly shaped to resemble wooden siding panels. It is often desired to impart to the exposed panel surfaces a simulated wood grain appearance. Conventionally, this has been accomplished by applying, over a pre-established paint coating on a metal strip surface, a pattern of lines or striations of a second color. The grain pattern thus produced, however, is preferentially vulnerable to wear and weathering since it is an overlay, and it has other disadvantages as well; for instance, when the pattern is applied from a roll having a paint-bearing wood-grain design of elevated or recessed portions formed on its surface, the same pattern repeats at regular, relatively short intervals equal to the circumference of the roll, unlike the appearance of actual wood grain which varies randomly and nonrepetitively.
Applicants' copending United States patent application Ser. No. 226,699, filed concurrently herewith, entitled "Coating Process and Apparatus" and assigned to the same assignee as the present application, describes certain strip-coating processes and apparatus of the general type employing a dam extending transversely across a major surface of a longitudinally advancing strip, with deposit of wet coating material on that strip surface immediately ahead of the dam, wherein, immediately beyond the dam, the strip is advanced longitudinally past a smooth and rigid wall (facing the coated strip surface) of extended length in the direction of strip advance, and at least as wide as the coated strip surface; during its advance past the wall, the strip is uniformly restrained against movement of its coated surface away from the wall by more than a predetermined distance equal to the desired coating thickness, so that the wall and strip mutually define a gap entirely filled with the wet coating layer. As explained in the aforementioned copending application, these features afford advantageously high uniformity of coating thickness even on strip which may be wavy-edged, oil-canned, or otherwise deformed. Moreover, the described arrangement provides better metering of the coating material than conventional techniques using rolls or doctor blades; substantially all the supplied coating material is usefully consumed to provide the desired coating, with virtually no loss due to spillage over the sides; and entrapment of air in the coating is avoided.
It would be desirable to provide, in conjunction with such coating techniques, means and methods for producing striped patterns that overcome the difficulties heretofore encountered in attempting, for example, to achieve a wood-grain appearance.